| 11. |
- Singh, Birendra, et al.
(författare)
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The unique structure of Haemophilus influenzae protein E reveals multiple binding sites for host factors.
- 2013
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Ingår i: Infection and Immunity. - 1098-5522. ; 81:3, s. 801-814
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Tidskriftsartikel (refereegranskat)abstract
- Haemophilus influenzae protein E (PE) is a multifunctional adhesin, involved in direct interactions with lung epithelial cells and host proteins, including plasminogen and the extracellular matrix proteins vitronectin and laminin. We recently crystallized PE and successfully collected X-ray diffraction data to 1.8 Å. Here we solved the structure of a recombinant version of PE and analyzed different functional regions. It is a dimer in solution and in the asymmetric unit of the crystals. The dimer has a structure that resembles a flattened β-barrel. It is however not a true β-barrel as there are differences in both the hydrogen bonding pattern and the shape. Each monomer consisted of a 6-stranded antiparallel β-sheet with a rigid α-helix at the C-terminal tethered to the concave side of the sheet by a disulfide bridge. The laminin/plasminogen binding region (residues 41-68) is exposed, while the vitronectin binding region (residues 84-108) is partially accessible in the dimer. The dimerized PE explains the simultaneous interaction with laminin and vitronectin. In addition, we found this unique adhesin being present in many bacterial genera of the family Pasteurallaceae and also orthologues in other unrelated species (Enterobacter cloacae and Listeria monocytogenes). Peptides corresponding to the surface-exposed regions PE24-37, PE74-89, and PE134-156 were immunogenic in the mouse. Importantly, these peptide-based antibodies also recognised PE at the bacterial surface. Taken together, our detailed structure of PE explains how this important virulence factor of H. influenzae simultaneously interacts with host vitronectin, laminin or plasminogen promoting bacterial pathogenesis.
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| 12. |
- Singh, Birendra, et al.
(författare)
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Vitronectin binds to the head region of Moraxella catarrhalis ubiquitous surface protein A2 and confers complement-inhibitory activity.
- 2010
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 75, s. 1426-1444
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Tidskriftsartikel (refereegranskat)abstract
- Summary The serum resistance of the common respiratory pathogen Moraxella catarrhalis is mainly dependent on ubiquitous surface proteins (Usp) A1 and A2 that interact with complement factor 3 (C3) and complement inhibitor C4b binding protein (C4BP) preventing the alternative and classical pathways of the complement system respectively. UspA2 also has the capacity to attract vitronectin that in turn binds C9 and hereby inhibits membrane attack complex (MAC) formation. We found UspA2 as a major vitronectin binding protein and hence the UspA2/vitronectin interaction was studied in detail. The affinity constant (K(D)) for vitronectin binding to UspA2 was 2.3 x 10(-8) M, and the N-terminal region encompassing residues UspA2 30-170 bound vitronectin with a K(D) of 7.9 x 10(-8) M. Electron microscopy verified that the active binding domain (UspA2(30-177)) was located at the head region of UspA2. Experiments with recombinantly expressed vitronectin also revealed that UspA2(30-177) bound to the C-terminal region of vitronectin residues 312-396. Finally, when human serum was pre-incubated with UspA2, bacteria showed significantly less serum resistance. Our study directly reveals the binding mode between the N-terminal domain of UspA2 and the C-terminal part of vitronectin and thus sheds light upon the mechanism of M. catarrhalis-dependent serum resistance.
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| 13. |
- Singh, Birendra, et al.
(författare)
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Vitronectin in bacterial pathogenesis: A host protein used in complement escape and cellular invasion.
- 2010
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 78:3, s. 545-560
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Tidskriftsartikel (refereegranskat)abstract
- The multifunctional human glycoprotein vitronectin (Vn) plays a significant role in cell migration, tissue repair and regulation of membrane attack complex (MAC) formation. It also promotes neutrophil infiltration and, thus, enhances the inflammatory process during infection. In the host, a balanced homeostasis is maintained by Vn due to neutralization of the self-reactivity of the MAC. On the other hand, Vn bound to the bacterial surface protects from MAC mediated lysis and enhances adhesion. Gram-negative bacterial pathogens including Moraxella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae use Vn recruitment to prevent MAC deposition at their surface. Moreover, Gram-positive bacterial pathogens such as Streptococcus pneumoniae and S. pyogenes utilize Vn for effective adhesion to host cells and subsequent internalization. Vitronectin has an Arg-Gly-Asp (RGD) sequence for binding the host cell integrin receptors and a separate bacterial binding domain for pathogens, and thus more likely functions to cross-link bacteria and epithelial cells. Once bacteria are attached to the vitronectin-integrin complex, various host cell-signalling events are activated and promote internalization. In this review, we focus on the important roles of vitronectin in bacterial pathogenesis and describe different strategies used by pathogens to evade the host response by the help of this intriguing molecule.
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| 14. |
- Singh, Birendra, et al.
(författare)
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Vitronectin in host pathogen interactions and antimicrobial therapeutic applications
- 2011
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Ingår i: Central European Journal of Biology. - : Walter de Gruyter GmbH. - 1895-104X. ; 6:6, s. 973-980
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Forskningsöversikt (refereegranskat)abstract
- Vitronectin (Vn) is a multifunctional glycoprotein profusely present in serum and bound to epithelial cell surfaces. It plays an important role in cell migration, tissue repair and regulation of membrane attack complex (MAC) formation. In the last decade the role of Vn has been extensively investigated in eukaryotic signalling and cell migration leading to the possibility of developing novel anticancer drugs. In parallel, several studies have suggested that pathogens utilize Vn in invasion of the host. Here we review the properties of Vn and its role in host-pathogen interactions that might be a future target for therapeutic intervention.
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| 15. |
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| 16. |
- Su, Yu-Ching, et al.
(författare)
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Haemophilus influenzae acquires vitronectin via the ubiquitous Protein F to subvert host innate immunity.
- 2013
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 87:6, s. 1245-1266
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Tidskriftsartikel (refereegranskat)abstract
- Acquisition of the complement inhibitor vitronectin (Vn) is important for the respiratory tract pathogen nontypeable Haemophilus influenzae (NTHi) to escape complement-mediated killing. NTHi actively recruits Vn, and we previously showed that this interaction involves Protein E (PE). Here we describe a second Vn-binding protein, a 30 kDa Yersinia YfeA homologue designated as Protein F (PF). An isogenic NTHi 3655Δhpf mutant devoid of PF displayed a reduced binding of Vn, and was consequently more sensitive to killing by human serum compared with the wild type. Surface expression of PF on Escherichia coli conferred binding of Vn that resulted in a serum resistant phenotype. Molecular analyses revealed that the N-terminal of PF (Lys23-Glu48) bound to the C-terminal of Vn (Phe352-Ser374) without disrupting the inhibitory role of Vn on the membrane attack complex. The PF-Vn complex actively delayed C9 deposition on PF-expressing bacteria. Comparative studies of binding affinity and multiple mutants demonstrated that both PE and PF contribute individually to NTHi serum survival. PF was highly conserved and ubiquitously expressed in a series of randomly selected NTHi clinical isolates (n = 18). In conclusion, the multifaceted binding of Vn is beneficial for NTHi survival in serum and may contribute to successful colonization and consequently infection.
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| 17. |
- Su, Yu-Ching, et al.
(författare)
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Impact of sequence diversity in the Moraxella catarrhalis UspA2/UspA2H head domain on vitronectin binding and antigenic variation
- 2013
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 15:5, s. 375-387
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Tidskriftsartikel (refereegranskat)abstract
- The nasopharyngeal pathogen Moraxella catarrhalis recruits vitronectin to subvert complement-mediated killing. Ubiquitous surface protein (UspA) 2 and its hybrid form UspA2H bind vitronectin at the highly diverse N-terminal head domain. Here we characterized the sequence diversity of the head domain in multiple M. catarrhalis clinical isolates (n = 51) with focus on binding of vitronectin. The head domain of the uspA2 genes from 40 isolates were clustered according to an N-terminal sequence motif of UspA2 (NTER2), i.e., NTER2A (55% of uspA2 variants), NTER2B (32.5%), NTER2C (5%), and finally a group without an NTER2 (7.5%). Isolates harbouring the uspA2H gene (n = 11) contained N-terminal GGG repeats. Vitronectin binding to isolates having UspA2 did not correlate to variation in the NTER2 motifs but occurred in UspA2H containing 6 or >= 11 of GGG repeats. Analyses of recombinant UspA2/UspA2H head domains of multiple variants showed UspA2-dependent binding to the C-terminal of vitronectin. Furthermore, polyclonal anti-UspA2 antibodies revealed that the head domain of the majority of Moraxella UspA2/2H was antigenically unrelated, whereas the full length molecules were recognized. In conclusion, the head domains of UspA2/2H have extensive sequence polymorphism without losing vitronectin-binding capacity promoting a general evasion of the host immune system.
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| 18. |
- Su, Yu-Ching, et al.
(författare)
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Moraxella catarrhalis: from interactions with the host immune system to vaccine development.
- 2012
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Ingår i: Future Microbiology. - : Future Medicine Ltd. - 1746-0921 .- 1746-0913. ; 7:9, s. 1073-1100
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Tidskriftsartikel (refereegranskat)abstract
- Moraxella catarrhalis is a human-restricted commensal that over the last two decades has developed into an emerging respiratory tract pathogen. The bacterial species is equipped with various adhesins to facilitate its colonization. Successful evasion of the human immune system is a prerequisite for Moraxella infection. This strategy involves induction of an excessive proinflammatory response, intervention of granulocyte recruitment to the infection site, activation of selected pattern recognition receptors and cellular adhesion molecules to counteract the host bacteriolytic attack, as well as, finally, reprogramming of antigen presenting cells. Host immunomodulator molecules are also exploited by Moraxella to aid in resistance against complement killing and host bactericidal molecules. Thus, breaking the basis of Moraxella immune evasion mechanisms is fundamental for future invention of effective therapy in controlling Moraxella infection.
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| 19. |
- Tamim, Al-Jubair, et al.
(författare)
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Haemophilus influenzae stores and distributes hemin by using Protein E.
- 2014
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Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 304:5-6, s. 662-668
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Tidskriftsartikel (refereegranskat)abstract
- The human pathogen Haemophilus influenzae causes mainly respiratory tract infections such as acute otitis media in children and exacerbations in patients with chronic obstructive pulmonary disease. We recently revealed the crystal structure of H. influenzeae protein E (PE), a multifunctional adhesin that is involved in direct interactions with lung epithelial cells and host proteins. Based upon the PE structure we here suggest a hypothetical binding pocket that is compatible in size with a hemin molecule. An H. influenzae mutant devoid of PE bound significantly less hemin in comparison to the PE-expressing wild type counterpart. In addition, E. coli expressing PE at the surface resulted in a hemin-binding phenotype. An interaction between hemin and recombinant soluble PE was also demonstrated by native-PAGE and UV-visible spectrophotometry. Surface plasmon resonance revealed an affinity (Kd) of 1.6×10(-6)M for the hemin-PE interaction. Importantly, hemin that was bound to PE at the H. influenzae surface, was donated to co-cultured luciferase-expressing H. influenzae that were starved of hemin. When hemin is bound to PE it thus may serve as a storage pool for H. influenzae. To our knowledge this is the first report showing that H. influenzae can share hemin via a surface-located outer membrane protein.
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| 20. |
- Voss, Sylvia, et al.
(författare)
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The Choline-binding Protein PspC of Streptococcus pneumoniae Interacts with the C-terminal Heparin-binding Domain of Vitronectin
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:22, s. 15614-15627
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Tidskriftsartikel (refereegranskat)abstract
- Adherence of Streptococcus pneumoniae is directly mediated by interactions of adhesins with eukaryotic cellular receptors or indirectly by exploiting matrix and serum proteins as molecular bridges. Pneumococci engage vitronectin, the human adhesive glycoprotein and complement inhibitor, to facilitate attachment to epithelial cells of the mucosal cavity, thereby modulating host cell signaling. In this study, we identified PspC as a vitronectin-binding protein interacting with the C-terminal heparin-binding domain of vitronectin. PspC is a multifunctional surface-exposed choline-binding protein displaying various adhesive properties. Vitronectin binding required the R domains in the mature PspC protein, which are also essential for the interaction with the ectodomain of the polymeric immunoglobulin receptor and secretory IgA. Consequently, secretory IgA competitively inhibited binding of vitronectin to purified PspC and to PspC-expressing pneumococci. In contrast, Factor H, which binds to the N-terminal part of mature PspC molecules, did not interfere with the PspC-vitronectin interaction. Using a series of vitronectin peptides, the C-terminal heparin-binding domain was shown to be essential for the interaction of soluble vitronectin with PspC. Binding experiments with immobilized vitronectin suggested a region N-terminal to the identified heparin-binding domain as an additional binding region for PspC, suggesting that soluble, immobilized, as well as cellularly bound vitronectin possesses different conformations. Finally, vitronectin bound to PspC was functionally active and inhibited the deposition of the terminal complement complex. In conclusion, this study identifies and characterizes (on the molecular level) the interaction between the pneumococcal adhesin PspC and the human glycoprotein vitronectin.
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